Pancreatic lipase exhibits selective esterase activity on carboxyl-linked hydroxycinnamic acid glucosides.

This study explores the susceptibility of phenolic acids (PAs) to digestion. 24 PAs were identified in apple, including 6 hydroxybenzoic acids (HBAs) and 18 hydroxycinnamic acids (HCAs), most of which were derivatives. PA derivatives showed distinct digestion patterns, clustering into groups. Group 1, with HBAs and HCAs esterified to glucose, had lower bioaccessible concentrations after the intestinal phase than Group 2, which included HCAs esterified to quinic acid or glycosylated via a β-O-glycosidic bond. Under different digestion conditions, the β-O-glycosidic bonds in ferulic acid 4-O-β-D-glucoside (FAG) and 4-hydroxybenzoic acid 4-O-β-D-glucoside resisted hydrolysis, while 6-O-feruloyl-d-glucose (FG), linked by an ester bond, was hydrolysed by pancreatin. When FG and its isomer FAG were digested with individual pancreatic enzymes (amylase, trypsin or lipase), FAG remained intact, whereas FG was hydrolyzed by lipase, mirroring pancreatin. Findings indicate a specific esterase activity of pancreatic lipase on HCAs esterified to glucose via a carboxyl ester bond.